Piston



. complished by providing it with a substantially- Patented July 7, 1936UNITED STATES PATENT OFFICE 8 Claims.

This invention relates to a piston having a compressible skirt withinherent spring tension adapted to operate within and conform to thewall of a cylinder, such as the cylinder of an internal combustionengine.

It has heretofore been the practice to so form the skirt of a pistonthat it will have some resiliency or give. Ordinarily this has beenaclongitudinal slot. The reason therefor is to compensate for variationsin expansion under heat between the material of the piston, generallyaluminum alloy, and that of the cylinder, generally cast iron. Onedifliculty with the usual type of split piston skirt is that it haslittle or "no inherent spring tension resulting in, its becoming setwith such clearance relative to the cylinder as to result in pistonslap, since this type of piston must be fitted with some clearance.Various methods have been devised for overcoming this difliculty byproviding the skirt with an expander adapted to exert an outwardpressure to maintain it in expanded cylinder contacting position. Othertypes of pistons are provided with a flexible steel skirt, but ofaconstruction which is generally light and flimsyand not sufficientlyfirm and rigid as to properly perform the required functions of thepiston skirt.

The object of this invention is to provide a piston not only with aflexible "-skirt, but one which will have inherent spring tension fornormallymaintaining it in a close, fit with the cylinder wall undercontinued operative conditions.

Furthermore, the skirt is of substantially normal character with theusual longitudinalsplit 'and is firm and rigid in respect to the pistonhead, although formed of a spring-like material, such as spring steel.

This may be accomplished by forming the skirt with an expansionformation along the edges of the split portion." 'In addition theretothere may be employed a spring web with a resilient formation tending tomaintain the skirt in its expanded position but permitting it to conformwith the cylinder wall. Such'a skirt may be cast integral with the head,otherwise permanently secured thereto, or removably attached.

As a result of this arrangement, the piston may be fitted to a cylinderwith the skirt in sliding contact, requiring no clearance. Aftersubstantial use, any wear will be taken up by the inherent springtension, whereby replacement, re-boring, or the use of auxiliaryexpanders would not be required. While maintaining the skirt in contactwith the cylinder, the tension would be sufiiciently light as not tocause resistance and heat generation by excessive frictional contact.

The full nature of the invention will be understood from theaccompanying drawing and the following description and claims:

Fig. 1 is a plan view looking at the bottom of the piston mounted in acylinder in compressed operative position. Fig. 2 is a section taken onthe line 22 of Fig. 1. Fig. 3 is a sectiontaken on the line 3-3 ofFig. 1. Fig. 4 is the same view as Fig. 1, showing a modified form ofpiston. Fig. 5 is a section taken on the line 5-5 of Fig. 4. Fig.6 isthe same view as Figs. 1 and 4, showing a second modification of thepiston. Fig. 7 is a fragmentary section taken on the line ll of Fig. 6.

In the drawing, reference being made to Figs. 1, 2, and 3, there isillustrated a cylinder ID in which the piston is mounted, said pistonbeing provided with the usual cast head ll of aluminum alloy or thelike, provided with the ring grooves l2, centrally formed web l3 anddownwardly extending wrist pin bosses l4 through which the wrist pin isadapted to extend, Fixedly secured to the flanges l5 of the bosses l4there is provided a pair of spring metal struts It, said struts beingformed adjacent one free end thereof with an expansion formation IT inthe form of an inwardly-extending fold. Said struts may be castintegrally with the boss portions, riveted, welded or otherwise fixedlysecured thereto.

' The piston skirt I8 is formed of spring'steel or a similar metal,preferably having inherent spring tension, and is to be distinguishedfrom aluminum or other more or less yieldable but not springy"metal.This skirt extends about the boss portions, and terminates adjacent thelower portion of the head I I, said skirt being of the usual length andconformation as that of the standard type of split skirt piston. Theskirt is suspended and carried by the ends of the struts l6, said endsbeing secured by rivet, weldings or otherwise, as indicated at I9.Intermediate the expansion formation ll of the struts, the skirt I8 issplit longitudinally thereof, the adjacent edges formed along the splitportion-thereof-being turned inwardly, as indicated at 20 to provide around exposed edge at the split of the skirt, and if so desired, providea further expansion formation which becomes effective under abnormalcompression and contraction.

From the foregoing, it will be understood that when-the skirt ofthepiston is in its operative variation in expansion and contractionbetween the skirt and the cylinder due to changes in temperature anddifference in metal, the skirt may be further compressed or will expandas the case may be, to maintain contact with the cylinder and preventpiston slap. This is accomplished through the flexibility and springtension exerted by the expansion formations ll of the struts and theformations 20 adjacent the split.

Figs. 4 and 5 illustrate substantially the same arrangement as abovedescribed, but wherein the bosses H4 are removably connected with thehead III through the medium of the sheet metal bracket I I2 whichextends upwardly and is removably secured to the under surface of thehead by the bolts H3, locked in position by the wire I I311. The bossesare provided with a flange H5 to which the struts I I6, as well as thesupporting bracket H2, are riveted. As above described, the struts areprovided with the formation III while the skirt I I2 is provided with asubstantially longitudinal slot I20. By this arrangement, the skirtstructure, together with the struts and bosses, may be separately formedand adapted to any piston head, if such arrangement is desirable. p

In the forms illustrated in Figs. 6 and 7, the

struts are eliminated, the expansive action and compression beingaccommodated by the inwardlyturned edges 220 of the skirt 2I8. The skirtin this modification is riveted or otherwise secured directly to thearcuately formed flanges 2 I5 of the bosses 2 I 4. The bosses areintegrally formed with the head 2| I. Under compression the spring steelskirt may be contracted by the yielding action of the abutting expansionformations 220 of the turned-in slotted portion. Said inwardly turnedportions 220 maybe so designed and formed as -to act as a springformation to any desired degree of compressibility.

The invention claimed:

1. A piston including a rigid head and a spring metal skirt connectedwith said head, said skirt being provided with a substantiallylongitudinal slot, the adjacent edges of the skirt defining said slotbeing curved inwardly in abutting relation to provide an expansionformation for permitting contraction of the skirt through their yieldingaction and exerting an expansive force under of an inwardly curved foldprovidedin each of said struts adjacent the split portion of the pistonfor normally exerting an" outwardpressure thereon while permittingcontraction thereof.

3. A piston including a rigid head and a depending skirt connected withsaid head, said skirt being provided with a substantiallylongitudinalslot, the adjacent edges of the skirt defining said slotbeing curved inwardly in abutting relation and formed of spring metal toprovide an expansion formation for permitting contraction of the skirtthrough their yielding action and exerting an expansive force underspring tension.

4. A piston having a rigid head with dependent bosses supportedtherefrom, a piston skirt having a substantially longitudinal slotformed therein, the free edges of said slot being formed of spring metaland extending inwardly in curved abutting f0rmation, spring metal strutssecured to said bosses and having their outwardly-extending free endssecured to said skirt, and an expansion formation provided in each ofsaid struts for normally exerting an outward pressure upon said skirtwhile permitting contraction thereof.

bosses supported therefrom, a skirt having a substantially longitudinalexpansion formation of spring metal formed therein extending from thebottom to the top of the skirt intermediate the bosses, spring metalstruts secured to said bosses and having their outwardly extending freeends secured to said skirt, and an expansion formation provided in eachof said struts for normally exerting an outward pressure upon the skirtwhile permitting contraction thereof.

6. A piston including a rigid head and depending substantiallycylindrical and flexible spring metal skirt, said skirt extending aboutthe entire periphery of the piston throughout substantially its entirelength but provided with a substantially longitudinal slot forpermitting it to be compressed and expanded under spring tension, and aspring metal strut securing said skirt to the head,

said strut being provided with a flexible spring formation for normallyexerting an outward pressure upon said skirt for increasing its radiusof curvature, while permitting compressionthereof against the inherentspring tension of said spring formation.

7. A piston comprising a head having a split skirt connected thereto,and longitudinally compressible flexible struts extending across saidskirt and connected thereto, the said skirt and struts being fabricatedwholly of spring steel.

8. As an article of manufacture, a bi-metallic piston of the separatehead and skirt type, the said skirt being carried by the head and formedwholly of spring metal and being split longitu- 25 5. A piston having arigid head with dependentdinally, and struts extending across andconnect- 60 ed to said skirt, the said struts being provided with meansexerting a continuous outwardly directed thrust on said skirt.

WALTER J. SIX.

